2-Pentadecyl-2-oxazoline alleviates anxiety-like behaviour and modulates the microbiota-gut-brain axis in obese mice

A bidirectional relationship between obesity and anxiety disorders has been increasingly associated with neuroinflammation and dysregulation of the gut-brain axis. Here, we investigated the pharmacological effects of the N-palmitoylethanolamine oxazoline derivative 2-pentadecyl-2-oxazoline (C15OXA) in a mouse model of high-fat diet (HFD)-induced obesity, with particular attention to its central and peripheral mechanisms of action. Male C57Bl/6J mice were fed an HFD for 12 weeks and subsequently treated with C15OXA (30 mg·kg^-1, p. o.) for 7 weeks. Behavioural, molecular, and microbiota analyses were performed to evaluate the effects of the compound. C15OXA significantly reduced anxiety-like behaviour in obese mice without affecting body weight, fat mass, or glucose tolerance. At the central level, C15OXA attenuated hippocampal neuroinflammation, as shown by reduced expression of COX-2, TLR4, NLRP3 and IL-1β. In parallel, C15OXA restored tight junction gene expression associated with blood-brain barrier integrity, and modulated unfolded protein response signalling. In addition, C15OXA enhanced markers of neurogenesis and synaptic plasticity. At the peripheral level, C15OXA treatment reduced colonic inflammation and improved gut barrier integrity. These effects were associated with a targeted reshaping of gut microbiota composition. In particular, C15OXA promoted the enrichment of butyrate- and menaquinone-producing bacteria, as taxa linked to beneficial metabolic functions. Overall, these findings suggest that C15OXA exerts anxiolytic-like effects associated with coordinated central and peripheral pathways involving the modulation of neuroinflammatory pathways, barrier integrity, and gut-brain axis signalling. This study provides novel pharmacological insight into the therapeutic potential of C15OXA for the treatment of obesity-associated neuropsychiatric disorders.